Interposed disk rheostat



Nov. 22, 1938. N. c, scr-IELLENGER INTERPOSED DISK RHEOSTAT Filed May l, 1933 5 .Sheets-Sheet 1 Inventor: Nea/Z072 Sc/zelleaer. #my JLMW..

fz/ ,6/gui Nov. 22, 1938. N. c. scHELLENGER 2,137,812

n INTERPOSED DISK RHEOSTAT Filed May 1, 1953 3 Sheets-Sheet 2 .[/UVZOT': Newton, a/zelleaer.

Nov. 1.938. c. SCHELLENGER 2,137,812

INTERPOSED DISK RHEOSTAT Filed May 1, 195s :s sheets-sheet s ulll'll/flllll 'l 204 200 zo@ 04 20a n -1- i-j 20a l oo u- 205 202 06 20 d FWZ. FIV' 75' i? f4' Newton Saiz e Z Z @72 er .TNT oFFIICE A `Newton C.' Schellengier, Elkhart, Ind.,-a'ss'ignorto -Chicago Telephone' Supply Company, a corpoifration offlndian'a Annamaria; 1, 1933, serial. @63u51 1o claims. (c1. zal-4s) lMyinvention relates tocontr'ol devices for electrical circuits. and, more particularlmto variable resistance devices o f the4 general typesetiorth in my prorPatent No. `1',85`1,933,.granted Mareh o29,1932.2 j

` The present application is directed towardimproving variable resistance .devices of ,the fintermediate contactdisk type, and especially those that are exceedinglysmall and Ac )mp act. Heretofore,..in the 'types of devices v.c :haraterized above. fit'. has ,been"'inpossible to obtain' `,a jclear,4 lsharp.,fxvve1lf defined line .of contact between the contacting` diskfand the resistance.A element. has been particularly v true IndeViceS'of-this .15` type .wherein the diameter. or width. of .s'u'ch'devices is'fqliite'snjiall; Qi. e., not'infexc'ess of-.three inches..` Thisfcondition has beenQdueto the fastei'iing means. employed .between `the contact ',disks @or ,20, rimsad their central' hubs;- 'These fastenings usually .'wer'e straight,l radial spokes', ,which .were necessarily short toconform with the requirements of the small mountings and casings within which they were assembled.

In the radial spoke typeof intermediate disk, when the rim is depressed intermediate any two of the spokes, the spokes bend at portions along their length. These increments of bent portions lie within, or parallel to, chords of a circle lying within the rim, and to whichchords-the longitudinal axis of the depressor arm isv always substantially normal. This action causes the entire segment of rim subtended by the major chord to be depressed downwardlytoward the resistance element, and a considerable amount of .the entire depressed segment actually engages the resistance element. Thus, if a substantially planar resistance element is employed, a fine', well defined line of contact cannot be effected, and a sensitive variation in resistance values is rendered impossible. Another diillculty in the prior art has been encountered in the connecting of flat, carbonaceous resistance elements to terminals by means of riv- 45 ets, screws, etc. It is necessary that some such fastenings be utilized to effect contact between the resistance element and the terminals at the high and low resistance ends of the element. This has been done heretofore by appropriating the extremeend portions of the resistance element to fasten, by means of large headed rivets that project above the contact surface.l the lresistance element and terminals to the base. This type of assembly necessitates the forfeiture of that por- 55 tion of the resistance element underlying the fastenings, as well as portions lying beyond'the fastenings, .which, of course, means a sacrifice of effective resistance.

Otherway's, equally as troublesome, have been tried .without success. One of these contemplated countersinking, a, cylindrially-headed rivet in a Y complementary aperture in thelbase, to permit the passage of the v,contactor member thereof., It was found, however, to .be impossible to obtain a Asmooth` eonnectionsurface between the rivet and the resistanceasince either the- Iivetheadwould Project meeneem-the .contacter-.prematurely to ,short-circuit,someeffective resistance, or .else it would fail toftouch at` all, .(being, countersunk too great..a, depth), wherebya high minimum resistance;y value resulted. at lthe low resistance termil'lal.

In combination variable resistance and power l switch units ,wherein both devices vare controlled .by a singleactuating shaft, there has heretofore been a further sacrifice of. effective resistance. The switch mechanism was caused to be actuated overfa portion of resistance elementadjacent the low resistance end, .which means that the switch 'was caused to open the circuit 4before maximum low resistance position couldbereached by the contactor; and, conversely, when the contactor was moved from the extreme low resistance position, a substantial amount of the resistance element was traversed before the switch was actuated to close the circuit. Thus, a considerable amount of otherwise effective resistance was rendered totally unusable.

Covers or housings for devices of the character described, and particularly those covers adapted to carry power switches, have been the source of much consternation and worry in the trade.

First, it was necessary to provide proper spacing means between the cover and the variable resistance device, to insure that parts of the switch and resistance device were in proper cooperative relation. Secondly, there had to be provided means to retain the cover in positive engagement with the variable resistance device to insure against any relative. movement therebetween. Thirdly, to position the cover, provision had to be made for terminals and other projections extending from the variable resistance device. These necessitated the provision of apertures, which permitted dust, dirt and other foreign matter to find its way into the casing to the detriment of the sensitiveparts therein contained.

Therefore, it is an object of my invention to provide a variable resistance device of the intercontacting disk for variable resistance devices of the interposed contacting disk type, that is highly flexible and which is capable of having peripheral portionsgdistorted out of theirnormal plane without distrbingftheposition`of its other portions.

It .isstill another object of my invention to proz vide a durable, inexpensive cover fora vvvariable resistance device, which has novel means for engaging the base of such device for retention there- 0D. ff 'r 'uw' -1 y invention to provide novel means for spacingl portions of a cover,

It is a further object of from portions of a variable resistance'device in predetermined relation, and to render said cover dust-proof.

' It is still'a further Object of my invention 'to `provide for fasteninga flat carb naceous resistance element to a base memberby'means lying within the path of the contactor of'a variable resistanc'e device "withoutA affecting the predetermined'reslstanc'e gradienfof the element.

It is still a further object of my invention to proi vide a combined variable resistance andfpower "'switch unit wherein thelswitch 'is actuated when f'por'tionf'of theeffective:resistance.r

' `With thabove andfelated 7objeictsi'n view, my inventiononsist's' in thjfollowing details'of construction Vand""combinationofpats;as will be 'more' fullyunderstoo'd from the'following speci- 'catiorr, "when 'r'ead in7 conjunction with theiaccompanying drawings, in which:

Figure' 1A is' va. perspective view of `la lvariable re- 'sistance device-'constructed in `accordance with :940 my invention. illustrated'with th'e'cov'er remQVed;

-' Figure 2'is`'a top'plan view of Figure 1;

Figure '3 is amid-sectional view of the variable resistance device and' 'cover having a switch l'mounted thereon 'the switch not being'shown in 45 section;

Figure '4 Ais anexploded vperspective view of the variable' resistance device and coverillustrating the relation of parts and order of assembly;

Figure is a' top plan view ofa modified form 50 of a pressure arm;

Figure '6 is a sectional view taken on the line 6-6'of Figure 5;

Figure 7 is a plan view of the pad holding blank;

Figure 8 is a side view of the modified pad 55 holder;

Figure 9 is a fragmentary exploded sectional view of a holding structure at each end of the resistance element;

Figure 10 is a fragmentaif assembled View of 60 the elements shown in Figure 11;

Figure 11 isy a` bottom plan view of the assembly shown in Figure 10, more y clearly showing the peened'over holding bolt;

Figure 12 is a modified form of pad holding 65 blank;

Figure "13 is a side elevational view of the modified pad holder made fromthe blank shown in Figure 12; andv Figure 14 is a bottom plan View of the modified T0 pad holder shown in Figure 13;

Referring in detail to the drawings: An insulating base A, generally circular in formation, has mounted upon one face I0, near its periphery, a 'circularly disposed resistance element B of the '75 lcarbonaceous type, although a wire wound resistsuitable bracket.- r

.Theil bushing C contains an enlarged head I6 disposed against the surface of the base upon which the resistance element is located, and if desired this head I6 may be serrated or knurled as shownat I8, 'see Fig. 3, so that it will bite into the basato prevent any relative rotary movement ,between-thebase and bushing.

I der 24disposed interiorly from vthe enlarged head I6 constrains an insulating washer'D 'upon which an interposed low resistance flat contactdisk E The meiske is preferably .cmrrisd'ofa .rim 26'. anda hubportion 28 which are'co'nnectedby a plurality offlexible s'erpentinetlspokesj. ,Ihe spokes are substantially Aof uniforml width from cumference." An electrical icox'rductr-"tabZ is formed upon thahub by Cuttiegwy, tha-Surrounding area. A plurality 'of positionin'g'j'ears l34 arejalso formed on the h ubby a punchpr'ess-operation,'an`d the ears tightlygrasp'notches 36in a'positioning 4insi'ilating washer F, to'prevent radialmovementjof the disk. The spokes are highly `flexible y and yieldable, and due to their serpentine configuration', are almost twice as long as they would be were they disposed alongv yradii of the diskthroughout their entire length. Thel increased length fof serpentine spokes over radial spokes increases the effective flexibility of the spokes'. The rim supported by them, being held by such highly flexible media, is permitted far greater freedomof'movement than has heretofore ever been possible.

The advantages of this increasedflexibility may better be seen by comparing these types of devices with those of the prior art. A rheostat of small diameter, having an interposed eontactor disc of the radial spoke type, will upon actuation of the contacter arm, short circuit a considerable amount of the effective resistance. The short, stiff spokes tend to hold the rim rigidly between them, whereupon, when the rim is depressed in one portion, a substantial segment of the rim is caused to follow the depressed portion to engage the resistance elementfor a considerable distance adjacent the contactor arm. Thus, a sharp or delicate line of contact is made-impossible, anda considerable amount ofthe effective resistance is short-circuited.

The serpentine spokes, however, permit the rim to be rather abruptly distorted out' o'f its normal pla-ne at the point 1of contact, without disturbing to anyrnaterial extent lthe'planar disposition of its`A remaining portion. In` this manner, a fairly sharp line of contact'is obtained, and

. a metalwasher may be placed over,the washer F to prevent breakage of the washer F provided it ismade ofzfragile materah l A pressureor wiper armG, ofthe general type shown in myapplication-flledLJanuary 31, 1930, Serial No..424,775,.which1has.matured into Patent No. 1,913,686,.may conveniently consist, of-a central portion =38 -secured to the end lof, a; shaft 39 as by'heading overthe splinedend- ,of-...the shaft. A- crescent-shaped arm 4tlhas its i ends yconnected tothel central portion Aby ',the, bight .portion 42. AAtongue 44,-;carrying a -pressure pad .-48 and projecting from the-.crescent arm 40,-'.is adaptedtostrike radially projecting; ears -46 of the cup-shaped housing or covering J, inorder to limit the rotation-.of the arm` n I.

The-pressure padmay fbe secure to y-theunder side of the arm andmayfhowever, take avariety of forms. In the form shown.-nFig. 4,.gthepad is formed of a cylindricalblock of material, such as .-oilA impregnated leather, andv :is held; in an inverted-eupin any-desiredimanner'.

In Figure-5, another modification of-,the pressure. arm;v and-@the pad` vholder.is -.shown. alignedopening 50 and anotch 52. .are,c'ut into -thef crescentfshapedzarm 40, and a :metal istrip isformed .to have one end'. 58 of iur-'shaped f through the lopening 5 0, The tongues IStand 64,

. potrusling :radially familles periphery f. "the 'providefa substantially dustproof vhc'usin'g,v to

guard any live pa`rts'from` coming into contact with the lhousing or s hell, and to cover the gap or .space between the housing and the terminals. lA plurality ofuslots 70 -in the liner K have the'jst'op members 46'of thehousing'ompletely passtherel through and Aoccupy the space dened therein.

The housing J; within which the" rheostat is housed, is providedf'witlil a v'pluralityof projecting tongues 12' ofy suiii'cientjlength to 'be bent over to attach the housing to the plate A.v4 A n elongated n'otch14 is out lin the free end of the cylindrical 'wall of the housing.' The base-A has an arcuate peripheral extension 16 through which suitable terminals pass and the peripheralV extension is constructed to intert with the notch "74 of the housing. -The' registration of the extension of the base and the notch 14 in the housing .with the plate A accurately'aligns the cover with respect to the'plateboth in a rotary direction about the axis ofrtheshaft and in a direc- -tlon along the shaft. f t e The elongated notch 'I4y of the housing J provides some clearance 'over the terminals to prevent any short circuit and the clearance is filled by the insulated strip liner K.

The liner `K,.is-of .such breadth that it will extend from the end wall portionof thefhousing J, down the innerface of lthe side vwalls -thereof to a peripheral line near their.open end. T his peripheral line Ais spaced from the free edge of the .'rnus ,"it will be segn'gtiiat the lower edge of' :the[li`ne r Vfornf'sra: bearing ,shoulder which abuts the-base.. member- .adjacert .theedge of its' inner .-.face and since `its upper'. edg, ,abuts the inner iaceof the endfwallpf the. housing', it'servesas,

.a spacer ,tomaiitain thelh'usingbaseland associatedparts in predetermined spacedffrelation. When y,the cover, is 'placedfonlghel basaso Athat notch .'l4.,`regis te`r 'swiththe 7terminal".mounting extension lof, the base, the"insulating`-1iner l strip K ,being ofthe samebreadth throughout, closely engagesthe basefmember around its periphery, angl closes ,thenOtch {1 4. `which.'over-lies the terminals.l The. IlinerVbein'g Aof flexible material, closely adheres `to allpitrtitns ofthebase, and adjusts itself toall .irregularities thereoforender the vergessenen The ears 12 arethenl e the base whereby a coin proof unit is prylde'dl f` fff-:The-.advantageaotfftlieiear .12.- iSt manifest in assemb1ineffthe-'-unit ruhen ...liner strip 1S emfplayedpress .that-crimes the ears finto engagement Awith th basefirst forces ,thefbase '-into,irmfeneagenientimith 'the adecco!- .linerK ,rand-then.@umts-the @ersteren tn .rmeintain the partein;thisrmfiengagementfSin. this isll n=f.,fa s ten.ing if meanafiand. vresults therefrom, A 1 Althoughftheresistance Aelement .base is annular in formation, the effectiveconducting surface of the resistance v-ele xrientzial arcuatee v in formation,l leaving. butl a small-'arc ineffective. small ,ineffective ,arcuate.distance-is-utilized for .the transient movement ofthe pressure arm duringtheclosing-of ,the switch. Heretofore, combined swit ches and variable resistance `devices have ,been s o constructed that the switch was actuated over an .effective portion of the resistance. Thus when. the contactor armwas moved 'from its point of lowestresistance, Athe switch moved toelosed position, but not before the contactor armhad traversed a substantial amount oi the effective resistance.. Lkewisawhen it was .desired tofmove the Ycontactor armvto its extreme low resistancepositionhe switch would be actuated-,intol open vposition to break .the cirycuit before this .couldbe effected. -f Consequently, a substantial amount .of the effective resistance was rendered useless. In my present structure, this fault is entirely overcome. A vItis essentialthat theentire upper surface of the resistance element base lies substantiallyin the same plane, otherwise the rim of the low resistanqe'mterposid-uisk will be bent and a kink permanently. established therein,

far; superior product The baseportionisprovicled with apertures 18` element having rivet apertures .of the same sizev pact, rigid and dusto'veriymg the base apertures 1a and 80,15 drawn -down into the tapered countersink by the tapered portion of the rivet head. The resistance elpassbeyond the effective resistance area during the actuation of the switch mechanism. The openingsg and 3 8 vthrough the conducting ends of the` resistanceelement, see Figs. 4,9 and 10, are'of the samediameter as the openings 18 and 80"thro gh the^base, andas the `rivets are of electricalco'nducting materialathe electrical circuit from theends'of the resistance element to the outside terminals 90 and92 will be completed.

In orderto prevent 'any damage to the resistance element great 'care mustjbe 'exercised in fastening'the rivets 82 and 84to the ends of the resistance element. l The most suitable manner is to expandthetip M of the bolt at a plurality of points 96, 98. |00, and |02 as shown in Figs. 9, 10 and 11.

A rivet |04fof conducting material, see Fig. 3,

attached to the tab '32 of the nexlbie disk-E and an intermediateelectrical terminal |06 provides "a rotary or oscillatoryfmovement of the pressure arm overa short peripheral length of the* circumference actuatesfbperably connected mechanism toopen or'close the snap switch.' However,

.the relationship f-theswitch to` the rheostat' is such that noneo'f theeifectiv'e conducting surface of the resistance element between the zero resistance, terminal e and the -maximum resistance terminal is contacted by the interposed member upon movment'ofthe pressure arm, during the operation of the'switch; A l

"In'fordertoprovide' for'the operation of the switch or circuit controller, the pressure or wiper arm G may be4 provided with a normally projecting, insulated,eccentrically mounted pin |08, see Figs. 1 and 3. This" pin |08 projects normalto the plane of the pressure arm G and into such position that it may transiently engage an operating ear |0 of the switch mechanism S. A transient movement of the pressure arm G will therefore operate the switch mechanism. The switch S, shown by-way offexample, may be any prei'erredf type of switch suitable for this purpose, such as for example the switch shown in my copending application Serial No. 602,006, filed March 30,1932, to which application reference is here made for the details of construction of the switch and the manner `of mechanical arrangement.

Terminals As will behest seen in Figures 1,2, 3 and 4, the terminal member |06, and the same details of construction apply to the yterminals 90 and 92, of a single strip of cor'xducting material of uniform thickness, has a foot ||2 connected, by means of the bolt, rivet, or eyelet 04 which pierces the base, tothe tab of the interposed disk which forms the intermediate variable contacting conductor. The foot 2 of the terminal is disposed upon the outer face of the base A and has a neck Ill therefrom bent normal to the plane of the base. The neck fits within a suitable slot ||6 in the mounting plate to prevent the terminalmember from being turned with respect to this plate. Shoulders ||8 and |20 extend from the neck Ill of suilicient width to rest and engage the opposite face of the mounting base A so that movement of the terminal in any direction is prevented. The shoulders then taper or merge into a lug portion until the notch or eye |22 is reached, thus when the various lead wires are being attached to the terminals there canl be' noinadvertent bending of any of the terminals so that the terminal rivets may be disturbed which-might result in ran'increased 4minimum resistance, particularly at the low'resistance end of -the resistance film;

' Furthermore, the terminal arrangement' hereinbefore described prevents the inadvertent pressing of the terminal against themetal panel for the radio set to complete a short-circuitwhich short-circuit may do considerable'damage during the testing or inspection of the radio set.

My preferred form of rlieostat` construction lends itself quite readily tothe tandem or double type of rheostat in which a second or -duplicate rhecstat structurels placed over the rst rheostat in place'of'the cover J. f'

In Figurel2 is shown another modification of the pad-holder blank.' lA tail 200merging into a body portion 202 has material for'wings 204`and 206 at each end adjacent a head portion 208. Upon forming the blank,'as shown in Figuresl3 and 14, thetail 2001s offset from fthe body 202 andthe head 208 is bent ina U-shaped formation which together with the wings '20( and 206 forms a basket or receptacle for the pad, which pad preferably may'have'- irregular sides.

Although this invention has been described-in considerable detail; such descriptionjis' intended as illustrative ratherthan limiting, as',the'inven tion may be variously embodied,y andthe scope of vthe invention is to be determined as claimed.

1. In a variable resistance unit, iii-combination, a base member, a resistance element mounted on said base member, a contactor device adapted to be moved to vary the eiective resistance 'of said element, and a metallic cup-shaped cover secured to said base member to overlie said resistance element and contactor device, theside wallsof the cup-shaped cover extendingbeyondfthe edges of the major portion of the base member, the cover being spaced relative to the base member by an upstanding cylindrical band of insulation disposed adjacent inner side wall portions ofsaid cover.

2. In a variable resistance device, a circular base member having a resistance element and a contactor mounted thereon, a cylindrical cupshaped casing telescoped snugly upon said base member to overlie said resistance element and contactor, the side walls of the cup-shaped cover extending beyond the edges of the major portion of the base member, a band of insulation disposed around the inner periphery of the side wall portion of the casing and being of less width than said side wall portion, the edge of said band adjacent the open end of the casing being adapted to engage the inner surface of said base member.

3. In a circuit controller unit, a base member having circuit controlling devices mounted thereon, terminal members projecting outwardly from said baser member, a metallic cover telescoped upon said base member having an aperture therein to provide clearance from terminal members, and a band of insulation interposed between portions of said cover and said-base member to mainilu tain a predetermined spaced relation therebetween and to close said aperture.

4. In a variable resistance device, a base member, a resistance and movable contactor carried thereby, a cup-shaped metallic casing, having ears depending from its free edge, telescoped upon said base member to overlie said resistance and contactor, a strip of insulation lining the side walls of the casing which is of less width than said sidewalls, the edge of said strip adjacent the open end of the casing adapted to engage the inner surface of said base member adjacent its edge, said ears being bent to engage the outer surface of said base at peripheral points to hold said strip and base member in firm engagement.

5. A variable resistance unit comprising a base member, resistance varying means mounted on said base member, a metallic cup-shaped cover telescoped upon said base member to overlie saidresistance varying means, a exible band of insulation disposedk around the inner face of the side walls of said cover, an edge of said band forming a yieldable bearing shoulder to engage said base member, a plurality of tongues extending from the free edge of said cover adapted to engage said base member to hold it in rmengagement with said yieldable bearing shoulder to eilectively seal said unit.

6. In combination, a variable resistance device comprising a base portion having a resistance and resistance varying means mounted thereon, a cover member therefor comprising an end wall, a side wall depending therefrom, said side wall having an irregular edge composed of apertures and ears, a flexible insulating strip disposed adjacent the inner face of said side wall spacing said cover from said base, said ears being crimped inwardly to engage said base portion to retain said cover thereon. f

7. A variable resistance unit comprisinga base member having a peripheral projection thereon, resistance varying means mounted on said base member, a shield telescoped snugly upon said base to overlie said resistance varying means, said shield comprising an end wall with side walls depending therefrom, a notch in the free edge of said side walls registering with said projection to prevent rotative movement between said shield and base member, a. plurality of ears integral with said side walls depending from said free edge, a cylindrical band of insulation surrounding said resistance varying means disposed entirely within said shield to forceably bear upon said base member adjacent the edge of its inner face, said ears being bent inwardly to engage the outer surface of said base member whereby said forceable engagement is maintained.

8. In a combined variable resistance and switch unit, a base member having resistance varying and switch actuating means mounted thereon, a cup-shaped metallic cover telescoped upon said base member to overlie said resistance varying and switch actuating means, a switch device mounted upon the end wall portion of said cover having a controller projecting therethrough, insulating means disposed between said base member and the end wall portion of said cover for effecting a predetermined spaced relation therebetween to permit cooperation between said controller and said switch actuating means, and a plu'rality'of fastening tongues extending from the free edge of said cover bent to engage said base member whereby the integrity of the unit; thus formed is preserved.

9. A rheostat comprising a base of insulating material, a peripheral extension on said base having extending edges, a plurality of terminal members, a plurality of recesses in said extension wherein each recess has a terminal member complementary therein, a cup-shaped metallic casing for said rheostat including a plurality of holding and positioning members extending from a peripheral edge of said casing, and two of said positioning members located immediately adjacent Athe edges of said peripheral extension whereby the casing is located in a predetermined position on said base.

10, In a combination rheostat and snap switch unit, a single control shaft Tor the unit, a base of insulating material, a resistance element mount-` ed upon said base, a peripheral extension on said base having a plurality of grooves therein, a plurality ofk complementary electrical terminal members interfltting into said grooves, a contact member for selectively engaging said resistance element, means for moving said contact member from said control shaft, means for operably connecting said terminal members to said resistance element and said contact member, a substantially cylindrical housing member having one end substantially closed, said substantially closed end having a small opening therein, a snap switch casing securely fastened to the substantially closed end of said cylindrical member whereby the snap-switch casing overlaps the cated in a predetermined position on said insulating base so that the snap switch trigger may be actuated by said eccentric.

NEWTON C. SCHELLENGER. 

